利用gs1.1和gs1.2突变体研究外源蔗糖对高铵胁迫拟南芥碳氮代谢的影响

以拟南芥野生型Col-0、谷氨酰胺合成酶敲除突变体gs1.1和gs1.2为实验材料,采取土培试验,比较正常培养液(4 mmol/L NH4⁺)培养(CK)、正常培养液(4 mmol/L NH4⁺)下外源添加5%蔗糖(T1)、高NH4⁺胁迫(20 mmol/L)(T2)以及高NH4⁺胁迫(20 mmol/L)下外源添加5%蔗糖(T3)对拟南芥各株系各生理指标的影响;通过测定地上部分的鲜重、叶绿素、游离NH4⁺、可溶性糖、可溶性蛋白、谷氨酰胺合成酶(GS)、谷氨酸脱氢酶(GDH)、矿质元素含量等指标,研究外源蔗糖对NH4⁺胁迫拟南芥碳氮代谢的影响。结果表明,高NH4⁺胁迫下,拟南芥生长受到严重的抑制,鲜重、GS、GDH酶活性降低,游离NH4⁺含量、叶绿素含量、可溶性糖和可溶性蛋白含量增加,植株的N、P、K、Ca的含量增加,Mg、Fe的含量减少,其中gs1.1和gs1.2在高NH4⁺处理下受到的抑制比Col-0更为显著。外源添加5%蔗糖显著缓解了高NH4⁺毒害,提高了可溶性糖和可溶性蛋白含量,提高了GS和GDH的活性,降低了叶绿素和游离NH4⁺的含量,提高了植株体内的N、P、K、Ca,Mg的含量,降低了植株Fe的含量,其中,外源蔗糖对gs1.1和gs1.2高NH4⁺毒害的缓解更为显著。

Effect of Exogenous Sucrose on Nitrogen and Carbon Metabolism of Arabidopsis Under High NH4+Stress Using gs1.1 and gs1.2 Mutants

Arabidopsis wild type Col-0, glutamine synthetase knockout mutants gs1.1 and gs1.2 were used as experimental materials, pot experiments were conducted to compare the effects of normal culture solution (4 mmol/L NH₄⁺) (CK), the normal culture solution (4 mmol/L NH₄⁺) plus additional 5% sucrose (T1), high NH₄⁺stress (20 mmol/L) (T2), and high NH₄⁺stress plus additional 5% sucrose (T3) on physiological indexes of the three Arabidopsis thaliana lines. By measuring the fresh weight of the aerial part, chlorophyll, free NH₄⁺, soluble sugar, soluble protein, glutamine synthetase (GS), glutamate dehydrogenase (GDH), and mineral element contents, the effects of exogenous sucrose on carbon and nitrogen metabolism in Arabidopsis thaliana under high NH₄⁺stress were preliminarily studied. The results demonstrated that Arabidopsis growth was severely inhibited under high NH₄⁺stress. The fresh weight, the activities of GS and GDH decreased, while the contents of free NH₄⁺, chlorophyll, soluble sugar and soluble protein increased, the contents of N, P, K and Ca in the plant increased, and the contents of Mg and Fe decreased. The inhibitory effects of gs1.1 and gs1.2 mutants under high NH₄⁺were more significant than the wild type. Exogenous addition of 5% sucrose significantly alleviated high NH₄⁺toxicity, with increased soluble sugar and protein contents, and enhanced the activities of GS and GDH. The contents of chlorophyll and free NH₄⁺were reduced. The contents of N, P, K, Ca and Mg in the plant were increased while the content of Fe was reduced. The exogenous sucrose is more significant in alleviation of high NH₄⁺toxicity of gs1.1 and gs1.2 than the wild type.